Ophthalmic surgeons start using navigation systems

Steinbeis experts carry out research on cataract and refractive eye surgery

Imaging diagnostics have been standard practice in orthopedic operations and interventional cardiology for years. These days, surgeons practicing oncology, ENT examinations and neurosurgery frequently use navigation systems to search for physical changes resulting from medical conditions. They also use them to precisely position implants. Experts at the International Vision Correction Research Centre, a Steinbeis Research Center at the University Eye Hospital in Heidelberg, are working in collaboration with Eyesight & Vision GmbH from Nuremberg on the possibilities and limitations of live “wavefront” defective vision measurements during operations. To this end, they are developing a navigation system for cataract and refractive surgery.

A micro-scanning mirror next to a matchstick

The navigation system in use on a surgical microscope

With more than 11 million operations carried out worldwide each year, the removal of aging and opacified lenses from the eye is the most common human surgical intervention. Over the past 60 years, the implantation of artificial interocular lenses (IOLs) has developed into a safe, minimally invasive procedure. Refractive lens surgery has made it possible to correct certain types of visual defects, allowing patients to once again see objects near and far without the need of glasses or contact lenses.

Research and development work in the field of refractive lens surgery revolves around two key areas. One is the ability to predict the refractive power of the eye more accurately by calculating IOL dimensions and selecting IOLs on a more individual basis. Researchers also want to find ways to correct more serious visual defects and thus make it possible to restore the correct perception of contrast and weak light.

The recent move toward wavefront abberometry is making it possible for ophthalmic surgeons to not only measure faulty vision after the removal of a lens with opacification, but also to measure the refractive power after an intraocular lens has been positioned in the eye. Until now, wavefront analysis involved projecting patterns of dots into the eyeball which were then used to diagnose imaging problems. As a rule, this approach did not work in the O.R. because the dot patterns were so baldy distorted by the defective vision that mapping the relative position of dots to one another was muddled or was sometimes actually impossible.

The technology recently put to use at the University Eye Hospital in Heidelberg and developed by the experts at the Steinbeis Research Center together with Eyesight & Vision GmbH solves this mapping problem with a laser beam. The laser beam can be cast quickly across the cornea to map the area. At any point in time, it is possible to identify the original source of a beam that has been altered in terms of its wavefront by the defective vision of the eye. This technology was made possible by a newly developed micro-scanning mirror which deflects laser beams pointed at it to map an area on the cornea and thus also on the retina.

The project team has made an important step forward in ophthalmic surgery. This technology makes it possible to make intraoperative defective vision measurements in real time. It thus lays a foundation for the development of a navigation system for refractive lens surgery.